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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6d71ef04b5e5d47484cbb62424c36f0a60af0647d4031a936ffeb729b8b14e1' 
  AND token = 'xXgV9a8Veyr3SNv2Z+uUueIFTy9YegziKQWCBTu0Gn8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}